1. Field of the Invention
The present invention relates to a construction of traveling devices of a swivel working vehicle like a crawler hydraulic shovel.
2. Related Art
Conventional arts about a form of a crawler for a crawler traveling device have been shown in Japanese Laid Open Gazettes Nos. Hei 8-53079, Hei 8-58647, 72759, Hei 8-85480, Hei 8-85482, Hei 8-91256, Hei 8-99656 and Hei 8-104262, for example.
A conventional crawler hydraulic shovel that is utilized as a swivel working vehicle is shown in FIG. 5. A swivel body F' is provided with a back-hoe including a bucket 4 and is mounted above left and right traveling devices K'. A rear end of swivel body F', when swivelled so as to be directed substantially perpendicular to the traveling direction of the traveling devices K', projects outwardly beyond the respective outer edge of the traveling device K'.
When the conventional swivel vehicle is carried by a small dump truck T, i.e., one of 2 or 4 capacity tonnage which can be driven by a common licensed driver to an excavating site, it is placed on a bed 2 of the dump truck T, as shown in FIG. 5, so that the swivel body F' is swivelled so as to direct the bucket 4 substantially perpendicularly to the traveling direction of the machine body. In this condition, a balance weight W1 on the rear end of the swivel body F' projects outwardly from one of the traveling devices K'.
As shown in FIG. 5, the swivel body F' is loaded with the balance weight W1 so that with respect to core metal projections 1a' of one of crawlers 1' a balanced point P' is defined. Thus, a part of the swivel body F' toward the balance weight W1 is balanced against the other part thereof toward the bucket 4 along balanced point P'.
In this construction, a distance b1 between the balanced point P' and the center of gravity of the balance weight W1 is set longer than a distance a1 between the balanced point P' and the center of gravity of the bucket 4, so that the weight balance between the part toward the bucket 4 and the part toward the balance weight W1 is maintained with the balance weight W1 being relatively light. The relationship between distances a1 and b1, and balance weight W1 and the weight of the swivel working machine toward the bucket, stabilizes the vehicle when it operates in the condition that the swivel body F' is swivelled so as to direct the back-hoe including the bucket 4 substantially perpendicular to the traveling direction of the traveling devices K', while the width between the traveling devices K' is small enough to fit on the bed 2 of the dump truck T.
On the other hand, a swivel working vehicle as shown in FIG. 3 has a small swivelling capacity and is constructed such that a rear portion of a swivel body F is formed into a circular shape and is disposed within a lateral width that extends between the outer edges of the traveling devices K. In this construction, the rear portion of the swivel body F does not project beyond the traveling devices K. However, when the swivel body F is swivelled so as to direct the back-hoe thereon including a bucket 4 substantially perpendicular to the traveling direction of the traveling devices K, it may become unbalanced due to the heavy weight of the bucket 4 and a bucket arm 5 against the balance weight W2. If the swivel body F becomes unbalanced, the machine body is apt to tilt toward the bucket 4, thereby causing the vehicle in operation to tumble or the vehicle placed on the bed 2 of the dump truck T to fall. Thus, the swivel working vehicle shown in FIG. 3 requires the balance weight W2 thereof to be considerably heavier than the balance weight W1 of the swivel body F' in FIG. 5 to prevent it from tumbling toward the bucket 4.
The conventional small swivel working vehicle shown in FIG. 3 that is provided with the balance weight W2, which is heavier than the balance weight W1, swivels and operates more advantageously in comparison with the vehicle shown in FIG. 5. However, it may not operate as well as an excavation working vehicle and is more expensive due to the weight of its balance weight W2.